SCIENCE CHINA Chemistry © Science China Press and Springer-Verlag Berlin Heidelberg 2013 chem.scichina.com www.springerlink.com *Corresponding author (email: zhumf@dhu.edu.cn)  ARTICLES  June 2013 Vol.56 No.6: 716–723 doi: 10.1007/s11426-013-4837-5 Synthesis and characterization of an environmentally friendly PHBV/PEG copolymer network as a phase change material XIANG HengXue, WANG ShiChao, WANG RenLin, ZHOU Zhe, PENG Cheng & ZHU MeiFang * State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China Received October 10, 2012; accepted November 6, 2012; published online February 21, 2013 Novel environmentally friendly poly(hydroxybutyrate-co-hydroxyvalerate) and poly(ethylene glycol) (PHBV/PEG) copolymer networks were synthesized through free-radical solution polymerization with PHBV diacrylate (PHBVDA) and polyethylene glycol diacrylate (PEGDA) as macromers. The molecular structure of PHBV/PEG copolymer network was characterized by Fourier transform infrared (FT-IR) and 1 H nuclear magnetic resonance ( 1 H NMR). The morphology of the PHBV/PEG co- polymer network was characterized by polarization optical microscopy. Thermal energy storage properties, thermal reliability and thermal stability were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis. The results indicated that the PHBV/PEG copolymer network hindered the growth of PEG crystalline segments or PHBV segments. PHBV/PEG copolymer network had a higher latent heat enthalpy, which didn’t reduce with the components of PHBV in- creased. Moreover, PHBV/PEG copolymer network still had good thermal stability even at 300 ℃. These results suggested that such environmentally friendly copolymer network would have wide applications in phase change energy storage materials. phase change material, environmentally friendly, energy storage material, copolymer network, PHBV, PEG 1 Introduction Phase change materials (PCMs) use the heat absorbed or released during melting and crystallization at certain tem- peratures [1, 2]. Their application fields include phase change energy storage fibers [3], body heat insulation [4, 5], solar energy storing materials [6], and drug delivery materi- als [7], etc. Over the past years, poly(ethylene glycol) (PEG) has become the choice polymeric material in PCM applica- tion and been used as energy storage and temperature con- trol material. However, the partial solid-liquid phase change of PEG induces poor process and shape stability. In order to obtain shape-stabilized or solid-solid PCM based on PEG, various supporting materials have been used to modify it via physi- cal and chemical methods. Among the former, porous or multilayer inorganic materials (such as montmorillonite, mesoporous active carbon, zeolite and silicon dioxide) and some organic polymers have been chosen to act as the sup- porting materials. Wang et al. [8] reported that polyethylene glycol/silicon dioxide composites were form-stable, solid- liquid PCM. There was no leakage of liquid PEG from the porous SiO 2 network due to the effect of capillary and sur- face tension forces. Karaman et al. [9] have injected PEG into the pores of diatomite using a vacuum impregnation method to prepare form-stable PCM. The maximum mass percentage of PEG confined in the diatomite was 50%. The freezing temperature and latent heat of the composite PCM are 32.19 °C and 82.22 J g 1 , respectively. Feng et al. [10] also reported shape-stabilized PCM composed of PEG and mesoporous active carbon (AC) which was prepared by a